The proposed study falls under "14. Personality in adulthood and old age; studies of stability and change in personality with age." The purpose of the proposed investigation is to explore stability and change in 20 aspects of adult personality as measured, at its widest interval, from age 34 to 74, in a longitudinally-studied sample of approximately 390 individuals. These individuals are original study members, or spouses or children of original study members, of the Berkeley Growth Study (BGS), the Guidance Study (GS), or the Oakland Growth Study (OGS). Responses to the California Psychological Inventory (CPI), a self-report measure of personality, provide the primary data to be analyzed. Since 1954, original study members have provided CPI data three (BGS) or four times (GS and OGS); members' spouses twice (BGS), three (OGS), or four times (GS); and members' children once (BGS) or twice (GS and OGS). Using hierarchical linear modeling, a statistical technique designed to accurately assess individual-level change and individual differences in individual-level change, the stability and change in personality from early to later adulthood will be explored. Three general research questions are posed: (1) which personality characteristics change and which do not?, (2) when does personality change and when does it not?, and (3) who shows personality change and who does not? For greater specificity and contextual understanding, gender and cohort differences in personality change will be examined. In addition, demographic and other personality data will be employed to begin to explain why aspects of personality may or may not change, when personality may or may not change, and who may or may not change.